Kesselring



Feb. 23, 1965 F. KESSELRING CONTROLLABLE ELECTRIC RESISTANCE DEVICES 2 Sheets-Sheet 1 Filed June 22. 1960 Feb. 23, 1965 F. KESSELRING 3,171,080

CONTROLLABLE ELECTRIC RESISTANCE DEVICES Filed June 22. 1960 2 Sheets-Sheet 2 Fig. 5

United States Patent D Claims. (01. 323-94 My invention relates to controllable electric resistance devices in which the resistor means proper consist of semiconducting material whose electric resistance is varied by subjecting the semiconducting resistor to a variable magnetic field.

It is known, for example, to expose semiconductor bodies of indium antimonide (InSb), indium arsenide (InAs) or other compounds of the A B type, as known from US. Patent 2,798,989, to a magnetic field and to utilize the dependence of semiconductor resistance upon the magnitude of the magnetic field for the purpose of controlling, regulating or switching operations. Suitable for the same purpose are other semiconducting compounds such as mercury telluride (HgTe) or other semiconductor compounds of the A B type. Particularly favorable, regardless of the semiconductor material being used, are rotationally symmetrical semiconductor bodies in which the electric current to be controlled passes radially through the semiconductor body, such magneticaln ly variable resistance devices being known from Patent 2,894,234, FIGS. 8 to 12. All of the known devices of this type are provided with a ferromagnetic core system with two pole shoes forming a field gap in which the semiconductor body is mounted.

With such magnet systems and ferromagnetic cores, an induction up to about 15,000 gauss is obtainable in the field gap under economically feasible conditions. This permits attaining a resistance change of approximately 1:50 under most favorable conditions. However the space requirements and cost of such a magnet system amount to a multiple of those of the semiconductor member proper. In devices of large size, the volumetric ratio of the magnet system inclusive of its excitation winding to the semiconductor may amount up to 100021. The great expenditure required for producing the magnetic induction has heretofore made such controllable resistance devices inapplicable for many purposes. Only with disc-shaped semiconductor components of slight thickness and a correspondingly narrow field gap in the ferromagnetic core system has it been possible to achieve a technologically and commercially useful change in electric resistance under economically satisfactory conditions. Such devices, however, require a difiicult and costly design due to the necessity of supplying current to the center electrode of the semiconductor disc between the narrowly spaced pole shoes, and the devices are applicable for small voltage current and power values only.

It is an object of my invention to devise a controllable magneto-electric resistance device with a semiconductor member subjected to a controlling magnetic field, in which the above-mentioned deficiencies are minimized or virtually eliminated.

Another object of my invention is to devise a magnetically controlled semiconductor resistance device capable of building up the magnetic field and hence changing the resistance within extremely short intervals of time, far below those required for the known devices mentioned above.

Still another object of the invention is to provide a magnetically controllable semiconductor resistance device ca- 3,171,080 Patented Feb. 23, 1965 ice pable of issuing or controlling abrupt current pulses for electronic firing or other pulse-generating purposes.

To achieve these objects, and in accordance with my invention, I provide the magnetic-field responsive semiconductor resistance member with an iron-less magnetic field system. That is, the magnetic field for controlling the change in semiconductor resistance is produced by an excitation coil of the type generally designated as aircored coil, the resistance member of semiconducting material being disposed in the field of such an iron-less excitation coil.

The foregoing and more specific objects and features of my invention, said features being set forth with particularity in the claims annexed hereto, will be described in the following with reference to the embodiments of devices according to the invention illustrated by way of example on the accompanying drawings in which:

FIGURE 1a is a diagonal cross section of FIG. 1b, FIG. lb is a front view, and FIG. 10 a schematic circuit diagram of a device in which the excitation and semiconductor components have an axially symmetrical design and a common radial center plane, a side view of the semiconductor components being separately shown in FIG. 1d;

FIG. 2a is a cross section of another embodiment of a semiconductor member, FIG. 2b a cross section 'of a group of such members interconnected in series relation, and FIG. 2c a cross section of another embodiment of an axially elongated semiconductor member, all applicable for the purposes of the invention;

FIG. 3 is a longitudinal sectional view of another em bodiment of the device of the invention;

FIG. 4a is a cross-sectional view of still another embodiment of a resistance device provided with two excitation coils, and FIG. 4b is a schematic circuit diagram including a device according to FIG. 4a; and

FIG. 5 is a graph explanatory of a resistance device as illustrated in FIGS. 11:, 1b, 1c, and 1d.

The device shown in FIGS. 1a, 1b and 1d comprises two discs 1 and 2 of indium antimonide which have respective central, inner terminal electrodes 3, 4 and a common ring-shaped outer electrode 5 extending over the outer periphery of both coaxially mounted discs. The ring electrode 5 is transversely slitted at 5a in order to prevent eddy currents. A circular insulating plate 6 is located between the discs 1 and 2. An excitation coil 7 is mounted in concentric relation to the disc assembly. The assembly of discs 1, 2 on the one hand, and the excitation coil 7 on the other hand, have a common radial center plane denoted by M in FIG. 1a.

In the embodiment of circuitry shown in FIG. 10, the ends of the excitation coil 7 are connected through a three-electrode spark gap device 8 with a capacitor 9 to be periodically charged, for example through a re sistor R, from current supply terminals T. The spark gap device 8 comprises an anode B, a cathode C and an ignition electrode Z. The ignition electrode is impressed by ignition voltage from a source 8a under control by a switch 8b. The terminal electrodes 3 and 4 are connected by respective leads 3:! and 4a with a current source S in series with a loadL. When the capacitor 9 is charged and the spark gap 8 is ignited, the capacitor 9 discharges through the coil 7 with the effect of producing in the discs 1, 2 a magnetic transverse induction. Relative to the center axis A of the semiconductor disc assemtion:

B gauss) wherein I denotes the instantaneous value of the current flowing in coil 7 in amperes, N the number of turns of coil 7, and d the median diameter of the coil in cm.

The change in resistance obtainable with the device according to FIGS. 1a, 1b, 1c, 1d is apparent from the graph in FIG. 5. Indicated on the abscissa is the magnetic induction in gauss. Indicated on the ordinate on a logarithmic scale is the change in ohmic resistance.

ductance of 240(ohm-cm.) and curve C relates to discs of the same material doped up to a conductance of 800(ohm-cm.) The outer diameter of these discs was 15 mm., the inner diameter was 4 mm., and the thickness of each was 4 mm. The excitation coil had 50 turns and a median coil diameter of 2.5 cm. The capacitor 9 used according to FIG. 10 had a capacitance of 400 microfarads.

It will be understood that a device according to FIG. 10 is applicable as a component of systems and networks in which the semiconductor resistance device serves to produce current pulses in the load for such purposes as providing the firing or ignition pulse for electronic switching tubes or electronic switching rectifiers or transistors, as well as to rvarious other purposes in which the issuance of a current pulse of relatively high intensity is desired. However, devices according to the invention are also applicable for longer lasting changes in ohmic resistance as are obtainable when applying to the excitation coil a correspondingly long lasting excitation voltage.

A pulse-controlled resistance device as exemplified by FIG. 10 is capable, with the aid of a sufficiently high capacitor voltage, to build up the magnetic field within extremely short intervals of time for example Within a few microseconds, aside from the advantage that the space requirements and cost of producing the resistance-controlling magnetic field are very small in comparison with known variable-resistance semiconductor devices heretofore known.

In the embodiment of FIGS. 1a, 1b, the excitation winding and the assembly of semiconductor discs are so arranged that they possess a common axis A and a common radial center plane M. This is necessary because, although the magnetic field in an air-cored coil is rotationally symmetrical, the induction at any selected point also depends upon the distance of this point from the center plane and upon the distance from the axis. The induction is greatest in the center plane m; it decreases with increasing spacing from the plane M, and increases with increasing spacing from the axis A in the direction toward the plane M. The resistance change of the disc is greatest with a rotationally symmetrical magnetic field.

The invention permits designing the resistance device in such a manner that the dimension of the semiconductor assembly in the direction of the symmetry axis, relative to the excitation-coil means, is at least substantially equal to, or larger than, the greatest diameter of the semiconductor assembly. This is illustrated by the embodiments shown in FIGS. 2b, 2c and FIG. 3. FIG. 2a shows an individual semiconductor disc 11 provided with a central, inner terminal electrode 13 and an outer, peripheral terminal electrode 14, similar to the semiconductor discs 1 and 2 described above with reference to FIGS. 1a, lb. ,According to FIG. 2b, a number of discs as shown in FIG. 2a are coaxially aligned and interconnected to jointly form a single semiconductor resistance assembly for a device otherwise designed and operative as described above. According to FIG. 2b, ten such discs 11 are joined together, each two mutually adlt cent discs having an outer electrode 15 or an inner electrode 16 in common. The current leads of the circuit in which the resistance assembly is to be used are to be attached to the terminal electrodes 13 and 17. Such a multiple disc assembly is particularly useful for high operating voltages. In other cases, a single solid hollow- The curve C relates to an InSb disc doped for a con- H cylindrical resistance body as shown in FIG. 20 is applicable. The hollow-cylindrical semiconductor body 18 is provided with a tubular inner electrode 19 and a likewise tubular outer electrode 20. The leads of the load circuit to be controlled are to be attached to the electrodes 19 and 20 respectively.

In the known variable-resistance semiconductor devices having a magnet system with a ferromagnetic core and a field gap adapted to the thickness of the semiconductor body, the inevitable stray field limits the attainable magnetic induction and hence the corresponding change in ohmic resistance to relatively small values. By comparison, the values of induction readily obtainable with devices according to the invention are much greater not only because of the reduced effect of stray fields but also because of the absence of ferromagnetic saturation.

Another example of a resistance device according to the invention in which the axial length of the semiconductor resistance body is larger than its greatest diameter is illustrated in FIG. 3. The rod-shaped semiconductor body 31, is provided with the inner electrode 32 consisting of a metal rod. The body 31 carries an outer tubular electrode 33 and is located in the interior of an axially elongated excitation coil 34. The radial center plane is located at the dot-and-dash line denoted by M. The change in ohmic resistance is elfected by varying the excitation of coil 34. The induction in such a cylindrical excitation coil is determined by the equation:

B=- (gauss) wherein L denotes the axial length of the coil in cm.

In lieu of a massive semiconductor body 31, as shown in FIG. 3, an assembly of coaxial semiconductor discs according to FIG. 212 may be used together with an axially elongated coil 34.

In a device as exemplified by FIGS. 1a and 1b, either the coil 7 or the assembly of semiconductor discs 1, 2 can be rotatably mounted so that it can be turned about a pivot axis passing perpendicular to the plane of illustration through the center point of the device on axis A. Such turning movement of one component relative to the other, for example in the direction of the arrow D, is then available for controlling the ohmic resistance of the device not only electrically as described above, but also by angular displacement of one component relative to the other. In such a device the resistance change eifected by a given excitation of coil 7 is greatest when the coil and the disc assembly are positioned as shown in FIG. 1a, whereas the rate of resistance change is reduced when the semiconductor assembly is turned out of the illus trated position.

A corresponding mechanical resistance control is obtained in a device of the type shown in FIG. 3 by making the semiconductor body 31 axially displaceable with respect to the coil 34, or vice versa. In the illustrated embodiment the rod 32 is shown displaceably mounted in fixed bearings 35, 36 to permit such displacement. It will be understood that in mechanically controllable devices, a desired change in resistance is also obtainable by mechanical means only, while maintaining the voltage of the excitation coil at a constant value.

The device illustrated in FIG. 4:: comprises a semiconductor disc 41 with terminal electrodes 42 and 43, an excitation winding 44, and another excitation wind- 1ng 45. As shown in FIG. 4b, the excitation winding 45 18 connected to a voltage source 46 through an adjustable resistor 48, whereas the excitationwinding 44 is connected to the source 46 in series with a load 47 and in series with the semiconductor disc 41. The resistor- 48 permits adjusting the current in the excitation winding 45 to a predetermined value of preexcitation so that the resistance of the semiconductor disc 41 assumes a predetermined value' when the load circuit is open. When the load circuit is closed, a current flows from source 46 through load 47 and also through the excitation winding 44 and the semiconductor disc 41. When for any reason the resistance of the load 47 increases, the current passing through the excitation coil 44 decreases accordingly. This causes a reduction in resistance of the disc 41. In this manner the device operates to regulate for constant current with a regulating performance virtually free of inertia.

Devices according to the invention as exemplfied by the embodiments described above can be modified and employed in various ways. Thus, for example, the excitation winding can be energized by alternating current of utility-line frequency or any desired higher frequency. When in such a case the semiconductor body or disc is connected to a direct voltage, an alternating current is produced in the circuit of the disc. If an alternating current is passed through the semiconductor resistance body, the device permits obtaining rectifying and modulating efiects.

I claim:

1. A controllable electric resistance device comprising a magnetic-field responsive resistance member of semiconductor material of substantially planar configuration and having a substantially circular cross section, said member having a peripheral electrode and a central electrode spaced from each other for passing current through said member, magnetic field means comprising an air-cored excitation coil of substantially circular cross section surrounding said member in coaxial relation thereto, and being positioned in a common diagonal plane with said members, whereby the resistance of said member between said peripheral and central electrodes is variable in dependence upon the excitation of said coil.

2. In a magneto-resistive device according to claim 1, said semiconductor resistance member and said excitation coil having respective radial center planes coincident with each other.

3. A controllable electric resistance device comprising a magnetic-field responsive resistance member of semiconductor material of substantially planar configuration having a circular cross section, said member having a central terminal electrode and an outer peripheral terminal electrode for passing current through said member, an air-cored excitation coil of circular shape coaxially surrounding said member and being positioned in a common radial center plane together therewith, whereby the resistance of said member between said terminal electrodes is variable in dependence upon the excitation of said coil.

4. In a magneto-resistive device according to claim 1, said semiconductor resistance member having an axial length at least as large as the largest diameter of said member.

5. In a magneto-resistive device according to claim 1, said semiconductor resistance member being constituted by a single semiconductor body.

6. In a magneto-resistive device according to claim 1, said semiconductor resistance member comprising a plurality of disc-shaped semiconductor bodies each having a central inner electrode and a peripheral outer electrode, said bodies being coaxially mounted in mutually spaced relation, each of said bodies being electrically interconnected at one of said inner and outer electrodes with the corresponding one electrode of a next adjacent body.

7. In a magnetoresistive device according to claim 1, said semiconductor resistance member and said field means being displaceable relative to each other for adjusting the rate of resistance change due to excitation of said field means.

8. In a magnetoresistive device according to claim 1,

said semiconductor resistance member and said field means being rotationally displaceable one relative to the other for adjusting the rate of resistance change due to excitation of said field means.

9. In a magneto-resistive device according to claim 1, said semiconductor resistance member having axially elongated shape and being axially displaceable relative to said field means for adjusting the rate of resistance change due to excitation of said field means.

10. A controllable electric resistance device comprising a magnetic-field responsive resistance member of semiconductor material of substantially planar configuration having a peripheral electrode terminal and a central elec trode terminal spaced from each other for passing current through said member, magnetic field means having an air-cored excitation coil in whose field said resistance member is disposed whereby the resistance of said member depends upon the excitation of said coil, said coil being positioned in a common diagonal plane with said member, an excitation circuit connected to said coil, and a load circuit connected to said terminals so as to include said member whereby said load circuit is controlled by the resistance variations of said member, said excitation circuit comprising current pulse generating means for shock excitation of said coil.

11. A controllable electric resistance device comprising a magnetic-field responsive resistance member of semiconductor material having two terminals for passing current through said member, magnetic field means having an air-cored excitation coil in whose field said resistance member is disposed whereby the resistance of said member depends upon the excitation of said coil, an excitation circuit connected to said coil, and a load circuit connected .to said terminals so as to include said member whereby said load circuit is controlled by the resistance variations of said member, said excitation circuit comprising current pulse generating means having capacitor means connected to said coil and having release means for shock discharging said capacitor means through said coil, whereby the magnetic field of said coil is built up within microseconds.

12. A controllable resistance device comprising a resistance circuit having a semiconductor member of substantially planar configuration having a peripheral electrode terminal and a central electrode terminal spaced from each other, air-core magnetic field producing means inductively linked with said semiconductor member for producing magnetic induction therein whereby the resistance of said resistance circuit is changed, said field producing means including a coil positioned in a common diagonal plane with said member and a pulsing circuit independent of said resistance circuit for controlling said field producing means.

13. A controllable resistance device as in claim 12, wherein said pulsing circuit includes a capacitor adapted to serve as a pulse current source and switching means connected to said capacitor including a spark-gap having two main electrodes and a firing electrode spaced from each other a distance such that the magnetic field in said field producing means is built up in the order of microseconds during discharge of said capacitor.

14. A controllable electric resistance device comprising a magnetic-field responsive resistance member of semiconductive material of substantially planar configuration having mutually spaced terminal electrodes for passing current through said member, and magnetic field means comprising an air-cored excitation coil of substantially annular configuration surrounding said member in coaxial relation thereto and positioned in a common diagonal plane with said member whereby the resistance of said member between said terminal electrodes is variable in dependence upon the excitation of said coil.

15. A controllable electric resistance device comprising a magnetic-field responsive resistance member of seiniconductive material of substantially planar configuration having an axis substantially perpendicular thereto passing therethrough and mutually spaced terminal electrodes for passing current through said member, and magnetic field means comprising an air-cored excitation coil of substantially annular configuration surrounding said member in coaxial relation thereto and. positioned with said member in a common plane substantially perpendicular to said axis, whereby the resistance of said member between said terminal eleotro-des is variable in dependence upon the excitation of said coil, said member and said coil being symmetrically positioned with relation to said common plane and with relation to said axis.

References Cited by the Examiner UNITED STATES PATENTS 2,549,775 4/51 Charchian 338 432 2,823,319 2/58 Vossberg 3201 X 2,894,234 7/59 Weiss et all 317234 X 2,924,633 2/60 Sichling et a1 32445 X 2,946,955 7/60 Kuhrt et a1 32445 X 2,964,738 12/60 Barney et a1 32445 2,996,655 8/61 Byles 324-45X LLOYD MCCOLLUM, Primary Examiner.

MILTON O. HIRSHFIELD, ROBERT L. SIMS, RALPH D. BLAKESLEE, Examiners. 

1. A CONTROLLABLE ELECTRIC RESISTANCE DEVICE COMPRISING A MAGNETIC-FIELD RESPONSIVE RESISTANCE MEMBER OF SEMICONDUCTOR MATERIAL OF SUBSTANTIALLY PLANAR CONFIGURATION AND HAVING A SUBSTANTIALLY CIRCULR CROSS SECTION, SAID MEMBER HAVING A PERIPHERAL ELECTRODE AND A CENTRAL ELECTRODE SPACED FROM EACH OTHER FOR PASSING CURRENT THROUGH SAID MEMBER, MAGNETIC FIELD MEANS COMPRISING AN AIR-CORED EXCITATION COIL OF SUBSTANTIALLY CIRCULR CROSS SECTION SURROUNDING SAID MEMBER IN COAXIAL RELATION THERETO, AND BEING POSITIONED IN A COMMON DIAGONAL PLANE WITH SAID MEMBERS, WHEREBY THE RESISTANCE OF SAID MEMBER BETWEEN SAID PERIPHERAL AND CENTRAL ELECTRODES 